1. Field of the Invention
The present invention relates generally to the field of wireless communications, and particularly to the design of an antenna.
2. Background
Small antennas are required for portable wireless communications. To produce a resonant antenna structure at a certain radio frequency and within a certain bandwidth, classical antenna structures need to have a certain volume. This volume becomes fairly large as the bandwidth required is large.
H. A. Wheeler, xe2x80x9cSmall Antennasxe2x80x9d IEEE trans. on Antennas and Propagation, Vol. AP-Jul. 23, 1975, provides a formula linking the volume of an antenna and the frequency. It is necessary to have a certain volume in order to obtain a desired bandwidth. In the case of a small portable device, a solution for maximizing the antenna volume, and hence the antenna bandwidth, is to wrap the antenna around the device.
Accordingly, the present invention addresses the need for a small compact antenna with wide bandwidth that can be integrated with a mobile device.
The present invention provides an antenna structure with the approximate characteristics of a slotted cylinder. Rather than utilizing a complete cylinder, the antenna structure utilizes a pair of spaced-apart patches that are joined together by one or more transmission lines that loop around with the same length as the perimeter of a corresponding cylinder. The antenna structure may be advantageously xe2x80x9cwrappedxe2x80x9d around an enclosure for an electronic device, such as a cellular telephone or the like.
In one form, the present invention provides an antenna comprising first and second conductive patches having respective first edges separated by a gap and having second respective edges; at least one conductor joining the respective second edges of the two patches, the conductor being routed in a loop away from the patches in a direction perpendicular thereto; and an antenna feed coupled to at least one of the patches.